x PREFACE. 



I hope these remarks will tend to encourage those who pursue knowledge, 

 whether with the energy of youth or the more steady enthusiasm of riper years ; 

 and as all nature, so all art, must ever be the result of those immutable pro- 

 portions and laws of action which it has pleased our Creator to impress on matter, 

 its objects are truly boundless. Our imperfection consists generally in not being 

 able to foresee all the circumstances which have an influence on the effects of 

 causes ; but in proportion as we proceed in knowledge, we also acquire greater 

 powers of perception : that which was at first difficult becomes easy, and the 

 mind is often roused by the bright gleam of truth, breaking as it were accidentally 

 upon a mass of obscure ideas, and rendering the true solution of the difficulty at 

 once obvious ; and as my gifted countryman Emerson has remarked, " the labour 

 and fatigue of seeking after it instantly vanishes." 



I proceed now to give some idea of this work. It appears to be large for its 

 object ; but, though confined to a single source of power, that power is gigantic, 

 and involves so many new and important doctrines in mechanical science and 

 practice, that it was impossible in justice to comprise it in less space. The work 

 is in Ten Sections. 



In the First, the history of the progressive improvement of the steam engine 

 is traced, from the period of its first suggestion by the Marquis of Worcester, to 

 its present state of high perfection. 



The Second Section presents an analysis of the nature of steam and of other 

 species of vapour ; the laws of their combination with heat, and of their elastic 

 force, density, and comparative power ; with the principles of calculating their 

 velocity when in motion, loss of force by cooling, &c. In this section it is shown 

 that water is of all other known fluids that best adapted for producing steam. 



The Third Section treats of the laws of combustion, and of the effect of different 

 species of fuel in producing steam ; the proportions of fire places and chimneys 

 of boilers, and the precautions necessary for their security and effect : the nature 

 and application of safety apparatus is fully discussed. The section closes with a 

 developement of the principles of condensing steam. 



In the Fourth Section, the power afforded by a given quantity of steam, and 

 all the methods of developing it, are illustrated both in a popular and scientific 

 manner; and the theoretical defect of the rotary action of steam is investigated. 



